1. Field of the Invention
The present invention relates generally to medical puncturing devices, and more specifically to lancets which are used to take blood samples from patients.
2. Description of Related Art
Lancet devices are used in the medical field for puncturing the skin of a patient to obtain a capillary blood sample from the patient. Certain diseases, such as diabetes, require that the patient's blood be tested on a regular basis to monitor, for example, the patient's blood sugar levels. Additionally, test kits, such as cholesterol test kits, often require a blood sample for analysis. The blood collection procedure usually involves pricking a finger or other suitable body part in order to obtain the blood sample. Typically, the amount of blood needed for such tests is relatively small and a small puncture wound or incision normally provides a sufficient amount of blood for these tests.
Various lancet devices are commercially available to hospitals, clinics, doctors' offices, and the like, as well as to individual consumers. Such devices typically include a sharp-pointed member such as a needle, or a sharp-edged member such as a blade, that is used to make a quick puncture wound or incision in the patient's skin in order to provide a small outflow of blood. It is often physiologically and psychologically difficult for many people to prick their own finger with a hand-held needle or blade. As a result, lancet devices have evolved into automatic devices that puncture or cut the skin of the patient upon the actuation of a triggering mechanism. In some devices, the needle or blade is kept in a standby position until it is triggered by the user, who may be a medical professional in charge of drawing blood from the patient, or the patient himself or herself. Upon triggering, the needle or blade punctures or cuts the skin of the patient, for example, on the finger. Often, a spring is incorporated into the device to provide the “automatic” force necessary to puncture or cut the skin of the patient.
It is of the utmost importance in the medical field that such medical puncturing devices or lancets are in a sterile condition before use. Today, generally without exception, medical puncturing devices or lancets are manufactured and packaged in a sterilized condition before they are distributed to medical professionals and members of the public who have a need for such devices. The sterile packaging maintains the sterility of the device, ensuring that the surrounding environment does not contaminate it until use. In addition, it is also of increasing importance that the user or another person does not come into contact with the needle or blade after use of the device. With the concern over blood-borne diseases, medical professionals are required to take great care with medical devices that come into contact with the blood of patients. Thus, an important aspect of lancet design involves preventing the needle or blade of the device from wounding the user or another person after the blood sample is drawn from the patient. Once used, the needle or blade should be shielded to prevent the needle or blade from wounding the user or another person handling the device. Moreover, the lancet device should be disposable to eliminate the chances of disease transmission due to the needle or blade being used on more than one person. In this regard, the lancet device should ideally be designed for one firing, and have safety features to prevent reuse.
Advances have been made in recent years to increase safety in operating and handling used lancet devices. For example, lancet devices are currently available which are single shot devices that feature automatic ejection and retraction of the puncturing or cutting element from and into the device. Examples of such medical puncturing devices are disclosed in U.S. Pat. Nos. 5,755,733; 6,432,120; and 6,248,120. U.S. Pat. No. 5,755,733 to Morita discloses a lancet device that includes a combined holder and lancet structure with a compressible zig-zag spring member that causes a lancet member to puncture the skin of a patient upon actuation of a pair of actuating arms. U.S. Pat. No. 6,432,120 to Teo discloses a lancet device including a lancet holder which contains a spring-loaded lancet structure with a single coil spring that effects the ejection and retraction of a lancet needle upon triggering of the structure. U.S. Pat. No. 6,248,120 to Wyszogrodzki discloses a lancet device comprised of a housing, a shielding portion, a piston with a puncturing tip, and separate drive and return coil springs that eject and retract the piston, respectively, upon the breakage of internal wing elements in the housing. Such assemblies include many components, and oftentimes utilize costly metal coil springs for activation.
U.S. Pat. No. 4,869,249 to Crossman et al. discloses a disposable lancet pricker having a body, a lance and an integrally molded zig-zag spring, which is activated by a separate cap inserted into the body. The zig-zag spring extends from the inner rear surface of the body to attach with the lance, and when compressed and released, causes the lance to project from and then retract back into the device. After use, the cap attaches with the lance to prevent further activation.
U.S. Pat. No. 6,136,013 to Marshall et al. discloses a lancet device formed from an integrally molded structure in a folded-out configuration. The device includes a two-part hinged housing with a button molded into one housing part and with a zig-zag spring hinged to the other housing part at the rearward end, with a lancet molded to the spring. The spring and lancet can be folded into the housing with the spring compressed, with the housing then closed to form the enclosed lancet. Activation is accomplished by laterally pushing the side button into the housing to release the compressed spring.
U.S. Pat. No. 5,630,828 to Mawhirt et al. discloses a disposable lancet having a housing, with a beam having a blade extending from one end and with the other end pivotally coupled to the housing. A trigger extends from a rear end into the housing, with activation involving pushing the trigger down into the housing to force the blade at the end of the beam spring to puncture the patient's skin, at which time the trigger is released to allow the beam spring to retract the blade back within the housing. Such a lancet involves the force of the user to puncture the skin, with the spring resulting in retraction of the lance.